Analysis of surrounding rock stability and support action in tunnels

ZHANG Dingli

doi:10.11860/j.issn.1673-0291.2016.04.002

Abstract：This paper is aimed at three basic problems in tunnel design:mechanical characteristics and load effect of surrounding rock,dynamic interaction of support and surrounding rock,syner-gistic action of supporting structure system.Firstly,based on statistical analysis of abundant mo-nitoring results in mountain tunnels,this paper put forward some general rules and basic charac-teristics of surrounding rock deformation.Taking deformation accelerating place of tunnel sur-face,application of initial supporting and secondary lining as three key nodes,this paper analyzed the mechanics evolution process of support and surrounding rock interaction.Then,a new con-cept was put forward in this paper:Shallow buried and deep buried surrounding rock form the composite surrounding rock structure.Through calculation and analysis,this paper described the dynamic characteristics of surrounding rock failure,and presented a method for determining the mode,mechanism and range of surrounding rock failure.By analyzing surrounding rock failure mode,this paper proposed that load effect is composed of given pressure from shallow buried sur-rounding rock and deformation pressure from deep buried surrounding rock,and then a formula for calculating the surrounding rock load acting on supporting structure is derived.Last of all, this paper established a mechanical model of the supporting structure system,analyzed the key factors that influence plastic zone development under elastoplastic model,and revealed the syner-gistic action of preliminary reinforcement layer and subsequent support layer.The research con-clusions are of great significance for the realization of dynamic and quantitative design as well as construction of tunnel engineering.